If agreement can’t be reached before 2030, the researchers say, a 2&degC target will be out of reach, the authors toldReuters.

Even an immediate price of $US20 per tonne of CO2 isn’t a guarantee of anything, the study’s authors explain: it only provides a 60 percent chance of keeping temperature rises to below 2°C.

The study, which also included researchers in Switzerland, New Zealand, Australia and Germany, found that the timing of greenhouse emission reduction is far more influential than any scientific uncertainty. And that means the politics is now far more important than anything that might pop up on denier blogs.

IIASA says if action is delayed, the outcome will include an urgent need to take coal-fired power generation offline.

If mitigation steps aren’t taken, the researchers say, global annual emissions by 2020 will reach 55 gigatons of CO2 each year. At that point, IIASA’s Keywan Riahi says, “you would need to shut down a coal power plant each week for ten years if you still wanted to reach the two-degree Celsius target”.

“Fundamentally, it’s a question of how much society is willing to risk,” says IIASA energy researcher and a co-author of the study, David McCollum. ®